JP2018149559A - Flux composition and solder paste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flux composition and a solder paste which can achieve good wettability of a solder alloy, and good reflow characteristics in a solder paste such as a stencil life, printability and suppression of voids in a solder joint, and ion migration on a substrate and suppression of insulation failure between wires (good insulation characteristics).SOLUTION: A flux composition contains (A) a base resin, (B) an activator, (C) a thixotropic agent, (D) a solvent, and (E) an indium complex.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a flux composition and a solder paste.

  As a method for joining an electronic component to an electronic circuit formed on a substrate such as a printed wiring board or a silicon wafer, a solder joining method using a solder alloy can be mentioned. At this time, a flux composition is generally used together with the solder alloy for the purpose of removing the solder alloy and the metal oxide on the substrate and improving the wettability due to a decrease in the surface tension of the solder alloy.

  Here, it is common to use lead as a solder alloy. However, since the use of lead is restricted by the RoHS directive or the like from the viewpoint of environmental load, it is becoming common to use a so-called lead-free solder alloy that does not contain lead in recent years. As such a lead-free solder alloy, Sn-3Ag-0.5Cu solder alloy is generally used in many cases.

  Since Sn-3Ag-0.5Cu solder alloy does not contain lead, it has a higher melting temperature (solidus temperature / liquidus temperature) than lead-containing solder alloy, and therefore wettability than lead-containing solder alloy. Is bad. In order to improve the wettability, there are methods for increasing the amount of the active agent blended in the flux composition or using a high heat-resistant active agent. In a solder paste using an alloy powder, the stencil life may be shortened and the storage period may be shortened.

  Further, the flux composition adheres to the solder joint portion or the vicinity thereof, for example, on the substrate or the terminal / lead frame of the electronic component when the electronic component is mounted on the substrate, and remains on the substrate after mounting as a flux residue. As for the flux residue, there are a cleaning method for cleaning the substrate after soldering and removing it, and a non-cleaning method for leaving it uncleaned. This non-cleaning method is preferable in that the cleaning step can be omitted.

  However, the remaining flux residue tends to cause corrosion, migration, etc. of the substrate. In particular, when a halogen-based activator is blended in the flux composition, anionic components such as halogens are likely to remain in the flux residue. Therefore, an electronic device incorporating a substrate having such a flux residue can be used for a long time. The occurrence of ion migration in the conductor metal is accelerated, and the risk of causing insulation failure between the wirings of the substrate increases.

  In order to improve the insulating properties of the flux residue and suppress the occurrence of ion migration, for example, a halogen scavenger is added to trap excess halogen ions floating in the flux, so that they exist on the board after soldering of electronic components. It can be attributed to ions such as halogen by adding flux and cream solder (see Patent Document 1) that can eliminate halogen ions to be generated, and inorganic ion exchangers that trap ions such as halogen and copper contained in the activator. Flux and cream solder for preventing ion migration (see Patent Document 2) are disclosed.

JP 7-171696 A JP-A-7-178590

However, the halogen scavengers and inorganic ion exchangers disclosed in these are inorganic fillers such as bismuth, magnesium, aluminum, zirconium, tin, antimony, titanium, and bismuth.
Here, when the flux which mix | blended the inorganic filler is used for cream solder, solder paste, etc., there exists a contradiction characteristic that the wettability of a solder alloy falls or a void tends to generate | occur | produce in the solder joint part formed. Therefore, the flux and cream solder (cream solder) disclosed in Patent Documents 1 and 2 improve the insulation properties of the flux residue, but have poor solder alloy wettability, and voids are formed in the formed solder joints. Problems such as being easy to do.

  Therefore, the compatibility between the solder flow reflow characteristics and the insulation characteristics such as solder alloy wettability, stencil life, and printability in the flux composition is an important item in the flux composition and solder paste, and has particularly high reliability. The demand for electronic devices such as in-vehicle electronic devices is expected to increase in the future.

  The present invention solves the above-mentioned problems. Good solder alloy wettability, stencil life, good reflow characteristics in solder paste such as printability and solder joint void suppression, and ion migration and inter-wiring between substrates It is an object of the present invention to provide a flux composition and a solder paste that can achieve both suppression of poor insulation (good insulation characteristics).

  In order to achieve the above object, a flux composition and a solder paste according to the present invention have the following configurations.

(1) The flux composition according to the present invention includes (A) a base resin, (B) an activator, (C) a thixotropic agent, (D) a solvent, and (E) an indium complex. Features.

(2) In the configuration described in (1) above, the amount of the indium complex (E) is 0.1% by mass or more and 1% by mass or less based on the total amount of the flux composition. .

(3) In the configuration described in the above (1) or (2), the indium complex (E) is a complex compound generated as a salt using an organic compound serving as a ligand for indium ions, The organic compounds are β-dicarbonyl compounds such as acetylacetone; amines such as ethylenediamine, pyridine and porphyrin; iminodiacetic acid, nitrilotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic acid, 1,2- Diaminocyclohexanetetraacetic acid, glycol etherdiaminetetraacetic acid, N, N-bis (2-hydroxybenzyl) ethylenediaminediacetic acid, ethylenediaminedipropionic acid, ethylenediaminediacetic acid, diaminopropanoltetraacetic acid, hexamethylenediaminetetraacetic acid, hydroxyethyliminodi vinegar Aminocarboxylic acids such as diaminopropanetetraacetic acid, nitrilotripropionic acid, ethylenediaminetetrakismethylenephosphonic acid; phosphonic acids such as nitrilotrismethylenephosphonic acid; stearic acid, palmitic acid, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, Saturated aliphatic carboxylic acids such as caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, margaric acid and 2-ethylhexanoic acid; unsaturated aliphatic carboxylic acids such as oleic acid and linoleic acid It is characterized by being at least one of aromatic carboxylic acids such as benzoic acid and phthalic acid.

(4) The solder paste according to the present invention includes the flux composition according to any one of (1) to (3) and a lead-free solder alloy.

  The flux composition and the solder paste of the present invention have good reflow characteristics in the solder paste such as good wettability of the solder alloy, stencil life, printability, and void suppression of the solder joint, and ion migration and inter-wiring between the substrates. It is possible to achieve both suppression of insulation failure (good insulation characteristics).

In the embodiment of the present invention and the comparative example, X-ray transmission is made through a general chip component mounting board to show “a region under the electrode of the chip component” and “a region where a fillet is formed” for observing the presence or absence of voids. Photo taken from the chip component side using the device.

  Hereinafter, one embodiment of the flux composition and solder paste of the present invention is described in detail. Of course, the present invention is not limited to the following embodiments.

(1) Flux composition The flux composition according to this embodiment comprises (A) a base resin, (B) an activator, (C) a thixotropic agent, (D) a solvent, and (E) an indium complex. Including.

(A) Base resin As the base resin (A), for example, (A-1) a rosin resin is preferably used.

  Examples of the rosin resin (A-1) include rosins such as tall oil rosin, gum rosin, and wood rosin; polymerization, hydrogenation, heterogeneity, acrylation, maleation, esterification, or phenol addition reaction of rosin. And a modified rosin resin obtained by subjecting these rosin or rosin derivative and an unsaturated carboxylic acid (acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, etc.) to a Diels-Alder reaction. Among these, a modified rosin resin is particularly preferably used, and a hydrogenated acrylic acid-modified rosin resin obtained by reacting and hydrogenating acrylic acid is particularly preferably used. In addition, you may use these individually by 1 type or in mixture of multiple types.

  The acid value of the rosin resin (A-1) is preferably 140 mgKOH / g to 350 mgKOH / g, and its weight average molecular weight is preferably 200 Mw to 1,000 Mw.

In addition to the rosin resin (A-1), a synthetic resin (A-2) can also be used as the base resin (A).
Examples of the synthetic resin (A-2) include acrylic resins, styrene-maleic acid resins, epoxy resins, urethane resins, polyester resins, phenoxy resins, terpene resins, polyalkylene carbonates, rosin resins having carboxyl groups, and dimer acids. Derivative compounds formed by dehydration condensation with a derivative flexible alcohol compound are exemplified. In addition, you may use these individually by 1 type or in mixture of multiple types. Among these, an acrylic resin is particularly preferably used.

  The acrylic resin can be obtained by, for example, homopolymerizing (meth) acrylate having an alkyl group having 1 to 20 carbon atoms or copolymerizing a monomer having the acrylate as a main component. Among such acrylic resins, acrylic resins obtained by polymerizing methacrylic acid and monomers containing two saturated alkyl groups having 2 to 20 carbon atoms in which the carbon chain is linear are preferably used. It is done. In addition, you may use the said acrylic resin individually by 1 type or in mixture of multiple types.

Regarding a derivative compound obtained by dehydrating and condensing the rosin resin having a carboxyl group and a dimer acid derivative flexible alcohol compound (hereinafter referred to as “rosin derivative compound”), as the rosin resin having a carboxyl group, for example, Rosin such as tall oil rosin, gum rosin, wood rosin; hydrogenated rosin, polymerized rosin, heterogeneous rosin, acrylic acid modified rosin, rosin derivatives such as maleic acid modified rosin, etc. Can be used. These may be used alone or in combination of two or more.
Next, examples of the dimer acid derivative flexible alcohol compound include compounds derived from dimer acid such as dimer diol, polyester polyol, and polyester dimer diol, and those having an alcohol group at the terminal thereof. For example, PRIPOL 2033, PRIPLAST 3197, PRIPLAST 1838 (manufactured by Croda Japan Co., Ltd.) and the like can be used.
The rosin derivative compound is obtained by dehydrating and condensing the rosin resin having a carboxyl group and the dimer acid derivative flexible alcohol compound. As the dehydration condensation method, a generally used method can be used. In addition, a preferred weight ratio when dehydrating and condensing the rosin resin having a carboxyl group and the dimer acid derivative flexible alcohol compound is 25:75 to 75:25, respectively.

  The acid value of the synthetic resin (A-2) is preferably 0 mgKOH / g to 150 mgKOH / g, and its weight average molecular weight is preferably 1,000 Mw to 30,000 Mw.

  Further, the blending amount of the base resin (A) is preferably 10% by mass or more and 60% by mass or less, and more preferably 30% by mass or more and 55% by mass or less with respect to the total amount of the flux composition.

  When the rosin resin (A-1) is used alone, the blending amount is preferably 20% by mass or more and 60% by mass or less, and 30% by mass or more and 55% by mass or less with respect to the total amount of the flux composition. More preferably. By setting the blending amount of the rosin-based resin (A-1) within this range, the flux residue can exhibit good insulation characteristics.

  Moreover, when using the said synthetic resin (A-2) independently, it is preferable that the compounding quantity is 10 to 60 mass% with respect to the flux composition whole quantity, and is 30 to 55 mass%. It is more preferable.

  Further, when the rosin resin (A-1) and the synthetic resin (A-2) are used in combination, the blending ratio is preferably 20:80 to 50:50, and 25:75 to 40:60. More preferably.

  As the base resin (A), it is preferable to use the rosin resin (A-1) alone or to use the rosin resin (A-1) and the synthetic resin (A-2) together. By using such a base resin (A), not only the initial insulation resistance of the flux residue but also the temporal insulation resistance can be kept good.

(B) Activator Examples of the activator (B) include carboxylic acids and halogen-containing compounds. You may use these individually by 1 type or in mixture of multiple types.

Examples of the carboxylic acids include monocarboxylic acids, dicarboxylic acids, and other organic acids.
Examples of the monocarboxylic acid include propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, capric acid, lauric acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, tuberculostearic acid, arachidic acid , Behenic acid, lignoceric acid, glycolic acid and the like.
Dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, fumaric acid, maleic acid, tartaric acid, diglycolic acid, 1,4-cyclohexanedicarboxylic acid An acid etc. are mentioned.
Examples of the other organic acids include dimer acid, levulinic acid, lactic acid, acrylic acid, benzoic acid, salicylic acid, anisic acid, citric acid, picolinic acid, and anthranilic acid.
In addition, you may use these individually by 1 type or in mixture of multiple types.
The carboxylic acids preferable as the activator (B) are preferably picolinic acid when used alone, and preferably mixed with picolinic acid, succinic acid and suberic acid when used in combination. (However, other carboxylic acids may be further mixed). Even in this case, it may be used by mixing with the halogen-containing compound.

Examples of the halogen-containing compound include a non-dissociable halogenated compound (non-dissociable activator) and a dissociable halogenated compound (dissociable activator).
Examples of the non-dissociative activator include non-salt organic compounds in which halogen atoms are covalently bonded. For example, chlorine, bromine, iodine, fluorine such as chlorinated compounds, brominated compounds, iodinated compounds, and fluorides. A compound having a covalent bond of each single element may be used, or a compound having a covalent bond of any two or all of these four elements may be used. In order to improve the solubility in an aqueous solvent, the compound preferably has a polar group such as a hydroxyl group such as a halogenated alcohol. Examples of the halogenated alcohol include brominated alcohols such as 2,3-dibromopropanol, 2,3-dibromobutanediol, 1,4-dibromo-2-butanol, and tribromoneopentyl alcohol; 2-bromohexanoic acid and the like Brominated organic acids; chlorinated alcohols such as 1,3-dichloro-2-propanol and 1,4-dichloro-2-butanol; fluorinated alcohols such as 3-fluorocatechol; and other similar compounds . You may use these individually by 1 type or in mixture of multiple types.
In addition, when the compound containing a halogen preferable as the activator (B) is used alone, 2-bromohexanoic acid is preferably used. However, even in this case, it may be used by mixing with the carboxylic acid or the like.

(C) Thixotropic agent Examples of the thixotropic agent (C) include hydrogenated castor oil, fatty acid amides, saturated fatty acid bisamides, oxy fatty acids, and dibenzylidene sorbitols. You may use these individually by 1 type or in mixture of multiple types.
The blending amount of the thixotropic agent (C) is preferably 2% by mass or more and 15% by mass or less, and more preferably 2% by mass or more and 10% by mass or less with respect to the total amount of the flux composition.
As the thixotropic agent (C), fatty acid amides are preferably used when used alone.

(D) Solvent Examples of the solvent (D) include isopropyl alcohol, ethanol, acetone, toluene, xylene, ethyl acetate, ethyl cellosolve, butyl cellosolve, hexyl diglycol, (2-ethylhexyl) diglycol, phenyl glycol, and butyl carbitol. , Octanediol, α-terpineol, β-terpineol, tetraethylene glycol dimethyl ether, trimellitic acid tris (2-ethylhexyl), bisisopropyl sebacate and the like. You may use these individually by 1 type or in mixture of multiple types.
The blending amount of the solvent (D) is preferably 20% by mass or more and 50% by mass or less, and more preferably 25% by mass or more and 40% by mass or less with respect to the total amount of the flux composition.
The solvent (D) is preferably hexyl diglycol when used alone.

(E) Indium Complex Examples of the indium complex (E) include those obtained by binding an organic compound serving as a ligand to indium ions, and commercially available products such as indium acetylacetone and indium tristearate can also be used. However, the said indium complex (E) may be produced | generated as salts using the organic compound used as a ligand.
A known method can be used as a production method when the indium complex (E) is produced as a salt using an organic compound. For example, when acetylacetone is bonded to indium ions using acetylacetone as a ligand, indium chloride chlorinated indium metal is heated in acetylacetone to synthesize an indium complex. In order to remove the by-produced hydrochloric acid, the solution containing the indium complex is separated into an organic phase such as ethyl acetate, diethyl ether, benzene, or toluene and an aqueous phase, and then indium acetylacetone dissolved in the organic phase is concentrated and The method of freeze-drying can be taken.

  Examples of the organic compound include β-dicarbonyl compounds such as acetylacetone; amines such as ethylenediamine, pyridine, and porphyrin; iminodiacetic acid, nitrilotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic acid, 1, 2-diaminocyclohexanetetraacetic acid, glycol etherdiaminetetraacetic acid, N, N-bis (2-hydroxybenzyl) ethylenediaminediacetic acid, ethylenediaminedipropionic acid, ethylenediaminediacetic acid, diaminopropanoltetraacetic acid, hexamethylenediaminetetraacetic acid, hydroxyethyl Aminocarboxylic acids such as iminodiacetic acid, diaminopropanetetraacetic acid, nitrilotripropionic acid, ethylenediaminetetrakismethylenephosphonic acid; nitrilotrismethylenephosphonic acid, etc. Sphonic acids: stearic acid, palmitic acid, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, margaric acid, 2-ethylhexanoic acid And saturated aliphatic carboxylic acids such as oleic acid and linoleic acid; and aromatic carboxylic acids such as benzoic acid and phthalic acid. In addition, the said organic compound may use individually by 1 type or multiple types.

Since the flux composition according to the present embodiment includes the indium complex (E), the indium complex (E) captures the ionic substance in the flux residue formed by using the indium complex (E). Can be suppressed.
In addition, since such a flux composition can ensure the wettability of the solder alloy without increasing the blending amount of the activator, etc., good reflow in solder paste such as stencil life, printability and suppression of voids in the solder joints. The characteristic can be exhibited.
Furthermore, the said indium complex (E) can suppress generation | occurrence | production of the solder ball | bowl generated on the electronic component side at the time of soldering rather than the indium as a metal element.

The compounding amount of the indium complex (E) is preferably 0.1% by mass or more and 1% by mass or less, and preferably 0.3% by mass or more and 0.7% by mass or less based on the total amount of the flux composition. More preferably, it is 0.4 mass% or more and 0.6 mass% or less. By controlling the blending amount of the indium complex (E) within this range, it is possible to further improve the effect of suppressing the deterioration of the insulation characteristics and the wettability and reflow characteristics of the solder alloy.
However, if the blending amount of the indium complex (E) exceeds 1% by mass with respect to the total amount of the flux composition, it is not preferable because voids are likely to be generated in the solder joint to be formed.

In the flux composition according to this embodiment, an antioxidant can be blended for the purpose of suppressing oxidation of the solder alloy to be used. Examples of the antioxidant include hindered phenolic antioxidants, phenolic antioxidants, bisphenolic antioxidants, and polymer-type antioxidants. Of these, hindered phenol-based oxidizing agents are particularly preferably used. You may use these individually by 1 type or in mixture of multiple types.
The blending amount of the antioxidant is not particularly limited, but generally it is preferably about 0.5% by mass or more and about 5% by mass or less based on the total amount of the flux composition.

An additive can be mix | blended with the flux composition which concerns on this embodiment as needed. Examples of the additive include an antifoaming agent, a surfactant, and a matting agent. You may use these individually by 1 type or in mixture of multiple types.
The blending amount of the additive is preferably 0.5% by mass or more and 20% by mass or less, and more preferably 1% by mass or more and 15% by mass or less with respect to the total amount of the flux composition.

(2) Solder paste The solder paste of the present embodiment is obtained, for example, by mixing the flux composition and an alloy powder made of a lead-free solder alloy.
The blending ratio of the alloy powder and the flux composition is preferably 65:35 to 95: 5 in the ratio of alloy powder: flux composition. The more preferred blending ratio is 85:15 to 93: 7, and the particularly preferred blending ratio is 87:13 to 92: 8.

  Examples of the lead-free solder alloy include Sn as a base material, Ag, Cu, Bi, In, Sb, Ni, Co, Fe, Mn, Cr, Mo, P, Ga, Ge, Zn, Cd, Tl, and Se. A lead-free solder alloy containing at least one of Au, Ti, Si, Al, and Mg can be used. Among these, an Sn—Ag—Cu-based lead-free solder alloy containing 90% by mass or more of Sn is preferably used.

  The average particle size of the alloy powder is preferably 1 μm or more and 40 μm or less, more preferably 5 μm or more and 35 μm or less, and particularly preferably 10 μm or more and 30 μm or less.

In addition to the solder paste, the flux composition of the present embodiment can be used for various soldering methods such as a flow method, a reflow method, and a solder ball mounting method.
And since the flux residue formed using the flux composition and the solder paste of the present embodiment has good insulating properties, it suppresses ion migration in the substrate and insulation failure between wirings, and also at the time of soldering, a solder alloy In addition, good reflow characteristics in solder paste such as stencil life, printability, and suppression of voids in solder joints can be secured.
Therefore, an electronic circuit board having such a flux residue can be suitably used for an electronic circuit board that is required to have high reliability, such as an in-vehicle electronic circuit board.

  Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples. The present invention is not limited to these examples.

Synthesis of acrylic resin A solution in which 10% by mass of methacrylic acid, 51% by mass of 2-ethylhexyl methacrylate, and 39% by mass of lauryl acrylate were mixed was prepared.
Thereafter, 200 g of diethylhexyl glycol was charged into a 500 ml four-necked flask equipped with a stirrer, a reflux tube and a nitrogen introduction tube, and heated to 110 ° C. Next, dimethyl 2,2′-azobis (2-methylpropionate) (product name: V-601, manufactured by Wako Pure Chemical Industries, Ltd.) as an azo radical initiator was added to 300 g of the solution from 0.2% by mass to 5%. Mass% was added to dissolve it.
This solution was added dropwise to the four-necked flask over 1.5 hours, and the components in the four-necked flask were stirred at 110 ° C. for 1 hour, and then the reaction was terminated to obtain a synthetic resin. The weight average molecular weight of the synthetic resin was 7,800 Mw, the acid value was 40 mgKOH / g, and the glass transition temperature was −47 ° C.

Preparation of Flux Composition Each component shown in Table 1 was kneaded to obtain a flux composition. In addition, unless otherwise indicated, the unit of the blending amount shown in Table 1 is mass%.

* 1 Hydrogenated acid-modified rosin manufactured by Arakawa Chemical Co., Ltd. * 2 Hindered phenol antioxidant manufactured by BASF Japan Co., Ltd. * 3 Zr / Mg / Al inorganic filler manufactured by Toa Gosei Co., Ltd.

Production of Solder Paste 11% by mass of each of the flux compositions and 89% by mass of the following lead-free solder alloy powders (powder particle size of 20 μm to 38 μm) were mixed, and Examples 1 to 4 and Comparative Examples were mixed. Example 1 to Example 4 and Comparative Example 1 to Comparative Example 4 and Comparative Example 6: Sn-3Ag-0.5Cu Lead-Free Solder Alloy Comparative Example 5: Sn-3Ag- 0.5Cu-0.2In lead-free solder alloy

(1) Insulation resistance test In accordance with JIS standard Z3284, a metal mask (comb electrode pattern) on a JIS2 type comb electrode substrate (conductor width: 0.318 mm, conductor interval: 0.318 mm, size: 30 mm × 30 mm) Each solder paste was printed using a slit processed to a thickness of 100 μm.
Then, each said board | substrate was obtained by heating each said board | substrate using the reflow furnace (Product name: TNP40-577PH, Tamura Seisakusho Co., Ltd. product). The reflow conditions at this time were: preheating at 170 ° C. to 180 ° C. for 75 seconds, peak temperature of 230 ° C., time of 220 ° C. or higher for 30 seconds, and cooling rate from peak temperature to 200 ° C. at 3 ° C. to 8 ° C./second. And the oxygen concentration was set to 1500 ± 500 ppm.
Next, each test substrate was put into a constant temperature and humidity tester (product name: small environmental tester SH-641, manufactured by Espec Co., Ltd.) set at a temperature of 85 ° C. and a relative humidity of 95%. The insulation resistance value 2 hours after the temperature and humidity reached the set value was measured as the initial insulation resistance value.
Then, the insulation resistance value is measured after a predetermined time has elapsed from the initial insulation resistance value measurement (after 100 hours, 200 hours, 300 hours, 400 hours and 500 hours), and the initial insulation resistance value and the predetermined time The minimum value (minimum insulation resistance value) of the insulation resistance values after the lapse was evaluated according to the following criteria. The results are shown in Table 2.
The insulation resistance value after a lapse of a predetermined time was measured by measuring the insulation resistance value 60 seconds after the measurement temperature in the constant temperature and humidity tester was 100 V.
○: Insulation resistance value is 1.0 × 10 ⁹ Ω or more △: Insulation resistance value is 1.0 × 10 ⁸ Ω or more and less than 1.0 × 10 ⁹ Ω ×: Insulation resistance value is less than 1.0 × 10 ⁸ Ω

(2) Void test A glass epoxy substrate (t = 3 mm) having a chip component having a size of 3.2 mm × 1.6 mm, a solder resist having a pattern capable of mounting the chip component of the size, and an electrode connecting the chip component. 1.6 mm) and a 150 μm thick metal mask having the same pattern was prepared.
Each solder paste was printed on the glass epoxy substrate using the metal mask, and 20 chip components were mounted on each solder paste.
Thereafter, the glass epoxy substrate is heated using a reflow furnace (product name: TNP40-577PH, manufactured by Tamura Corporation) to electrically bond the glass epoxy substrate and the chip component to each other. Each test substrate on which the chip component was mounted was formed. In this case, the reflow conditions are as follows: preheat is 170 ° C. to 190 ° C. for 110 seconds, peak temperature is 245 ° C., time of 200 ° C. or higher is 65 seconds, time of 220 ° C. or higher is 45 seconds, and cooling from peak temperature to 200 ° C. The rate was 3 ° C. to 8 ° C./second, and the oxygen concentration was set to 1500 ± 500 ppm.
Next, the surface state of each test substrate was observed with an X-ray transmission device (product name: SMX-160E, manufactured by Shimadzu Corporation), and the area under the electrode of the chip component at each solder joint (FIG. 1A). Area) and a void area ratio (total void area / land area × 100) in the area where the fillet is formed (area occupied by (b) in FIG. 1) were calculated and evaluated as follows. The results are shown in Table 2.
○: Void area ratio is 10% or less △: Void area ratio is more than 10% and less than 15% ×: Void area ratio is 15% or more

(3) Solder ball test Each test substrate was prepared under the same conditions as in the above (2) void test except that 20 chip parts having a size of 2.0 mm × 1.2 mm were used.
Next, the surface state of each test substrate was observed with an X-ray transmission device (product name: SMX-160E, manufactured by Shimadzu Corporation), and the number of chip components in which solder balls were generated around the periphery was calculated. It was evaluated as follows. The results are shown in Table 2.
○: Less than 5 Δ: 5 or more and 10 or less ×: 11 or more

As described above, since the above example contains a predetermined amount of indium complex (E) in the flux composition, the flux residue formed despite the incorporation of a halogen-containing compound as an activator. It can be seen that since the indium complex (E) captures the ionic substance, both can exhibit good insulating properties and a solder ball suppressing effect, and can also exhibit a void suppressing effect. On the other hand, in Comparative Example 6 in which the indium complex (E) is blended in an amount of more than 1% by mass, it can be seen that good insulation characteristics and a solder ball suppressing effect can be exhibited, but voids are easily generated in the formed solder joint. .
In addition, as shown in Table 2, in Comparative Example 5 using the lead-free solder alloy with In added, the solder ball suppressing effect is not sufficient, and by adding the indium complex (E) to the flux composition, It can be seen that the effect can be exhibited.

As mentioned above, the flux composition and solder paste of this invention can be used suitably also for the electronic circuit board | substrate with which high reliability is calculated | required, such as a vehicle-mounted electronic circuit board | substrate. Furthermore, such an electronic circuit board can be suitably used for an electronic control device that requires higher reliability.

Claims (4)

  A flux composition comprising (A) a base resin, (B) an activator, (C) a thixotropic agent, (D) a solvent, and (E) an indium complex.   The flux composition according to claim 1, wherein the compounding amount of the indium complex (E) is 0.1% by mass or more and 1% by mass or less based on the total amount of the flux composition. The indium complex (E) is a complex compound produced as a salt using an organic compound that becomes a ligand for indium ions,
The organic compounds are β-dicarbonyl compounds such as acetylacetone; amines such as ethylenediamine, pyridine and porphyrin; iminodiacetic acid, nitrilotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic acid, 1,2- Diaminocyclohexanetetraacetic acid, glycol etherdiaminetetraacetic acid, N, N-bis (2-hydroxybenzyl) ethylenediaminediacetic acid, ethylenediaminedipropionic acid, ethylenediaminediacetic acid, diaminopropanoltetraacetic acid, hexamethylenediaminetetraacetic acid, hydroxyethyliminodi Aminocarboxylic acids such as acetic acid, diaminopropanetetraacetic acid, nitrilotripropionic acid, ethylenediaminetetrakismethylenephosphonic acid; phosphones such as nitrilotrismethylenephosphonic acid Stearic acid, palmitic acid, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, margaric acid, 2-ethylhexanoic acid, etc. 3. A saturated aliphatic carboxylic acid such as oleic acid and linoleic acid; and at least one aromatic carboxylic acid such as benzoic acid and phthalic acid. 2. The flux composition described in 1. A solder paste comprising the flux composition according to any one of claims 1 to 3 and a lead-free solder alloy.